UHI study of the UK Armagh Observatory

Click image for interactive panorama take from the top of the meteorological tower

Via Dr. Roger Pielke Sr. and with a h/t to Erik, I found this most interesting, because it demonstrates the even small things like hedges can influence temperature readings. This paper originally had only 1 diagram, but I’ve added photography to help you visualize the site.

“Within a few weeks of the commencement of the experiment, it became apparent that at one of the selected sites there were irregularities in the pattern of temperatures observed. The night-time minima at site B (fig.1) were generally 1-2°C lower and the day-time maxima 1-2°C higher than the other rural stations. In view of this, the thermometers at all three rural stations were tested by the Met.Office and were subsequently found to be accurate to within 0.1°C.

It was found that site B was over-sheltered by nearby dense hedges and thus there was little air turbulence, even on breezy days. At night, cold air was ‘ponded’ by the hedges and this produced the abnormally low minima at site B compared to the other stations. The site was also located about 100m from,
although approximately 10m above, an extensive area of flat marshy land. This factor may have further contributed to the anomalous temperatures.”

1 Department of Environmental Sciences, University of Ulster, Coleraine, N.I.

2 Armagh Observatory, College Hill, Armagh BT61 9DG, N.I.

1. Introduction

Meteorological observations have been made at Armagh Observatory (Butler and Johnston, 1996) since 1795. The records include one of the longest single-site instrumental temperature series in the UK and, indeed, Europe.

The Observatory is situated in 20 acres of land on a drumlin to the North East of Armagh town centre (Fig.1). The grounds surrounding the Observatory and its climate station have remained relatively unchanged over the past 200 years. However, in that time, the town of Armagh has spread in several directions, including to the north and east, past the Observatory site. Much of the development around the site has been in the form of housing built over the past 20-30 years and this development still continues.

Amagh automatic weather station - Click for info - note the panorama above was taken from tower top

It is a well documented fact that urban areas can cause localised climatic modification (eg. Oke 1987; Ripley et al.1996). One of the most obvious ways in which the local climate may be altered is in higher night-time air temperatures in the built up area as compared to the surrounding countryside. This “heat island” may result in minimum urban temperatures 5-6oC greater than those of the surrounding rural area, in the early hours of calm, clear, nights in large cities (Barry & Chorley 1992).

With a population of around 14,000, Armagh, in UK terms, would be classed as a small town. Nevertheless, due to the fact that the built up area has extended beyond the Observatory site in the time during which instrumental meteorological observations have been made, the question of a possible non-climatic influence upon observed temperatures has to be considered.

2. Observations

In order to quantify the influence that urbanization may exert over air temperatures at the Observatory climate station, a comparative trial was initiated in February 1996.

Using equipment loaned to the Observatory by the Met. Office, three weather stations, A,B and C (Fig.1), were installed in rural locations, each approximately 1-2km from the urban boundary. The sites for these stations were carefully chosen to be as similar as possible to that of the Observatory climate station, O (Fig.1), to minimize any differences due to variations in shelter, topography, exposure, etc.

This required that each site be around 60m O.D., on a south facing slope with a grassy surface. In addition, it had to be reasonably accessible by road.

Following selection according to these criteria, Stevenson screens and rain gauges were installed on three suitable sites under the supervision of the Met. Office, on 22nd February 1996. To eliminate artificial temperature variations caused by the proximity of animals, a wire fence encircling each station, was constructed.

Observations commenced the following morning and, throughout the trial period, were timed, as far as possible, to coincide with the observations at the Observatory, bearing in mind that the total distance between stations was around 20km. Even so, the first readings were taken no more than 20 minutes before and the final readings no more than 20 minutes after the Observatory readings each day. Thus any bias which the slight differences between observing times may have introduced was kept to a minimum. A record of maximum and minimum air temperatures, wet and dry bulb temperatures and rainfall was made each morning at each station. However, when the daily maximum or minimum temperature occurred close to the time of observation, the readings for these days were excluded from subsequent analysis.

Within a few weeks of the commencement of the experiment, it became apparent that at one of the selected sites there were irregularities in the pattern of temperatures observed. The night-time minima at site B (fig.1) were generally 1-2oC lower and the day-time maxima 1-2oC higher than the other rural stations. In view of this, the thermometers at all three rural stations were tested by the Met.Office and were subsequently found to be accurate to within 0.1oC.

It was found that site B was over-sheltered by nearby dense hedges and thus there was little air turbulence, even on breezy days. At night, cold air was ‘ponded’ by the hedges and this produced the abnormally low minima at site B compared to the other stations. The site was also located about 100m from, although approximately 10m above, an extensive area of flat marshy land. This factor may have further contributed to the anomalous temperatures.

Following our appreciation of these difficulties, another site, D (Fig.1), to the southwest of Armagh Observatory was selected close the ancient earthworks known as The Navan Fort. Again, the physical characteristics of the site were similar to those of the Observatory station. The equipment from site B was installed at site D, again under Met.Office supervision. Readings obtained at this site, subsequently were found to be more consistent with those from the other two rural sites.

3. Results

In Figure 2 we show the differences in daily maximum and minimum temperatures, between the Observatory and the mean of the three outlying rural stations (A,C,D). We note that, apart from an overall zero point difference, there is little evidence for a trend in the differences with temperature. In Table 1, the mean differences are listed. The observations made at site B and those which were made close to the time the maximum or minimum temperature occurred have been excluded from these results.

Table 1.

Mean temperature differences between Observatory (O) and the mean of the three rural (R) stations (A,C & D), February to October 1996

Means

O

R

O-R

deg.C

tmax

14.63

14.52

0.11

tmin

6.9

6.53

0.41

The mean difference in daily maxima between the Observatory and the mean of the three rural stations is found to be 0.11oC, whilst the difference in minima is 0.41oC, with the Observatory station warmer than the mean of the rural stations in both instances.

4. Discussion

Taken at face value, the above results indicate that a temperature differential exists between the site of the Observatory weather station and similar sites in a rural location. However, at the outset, it was stated that the aim of this work was to assess any influence the urban development of Armagh City around the Observatory site might exert on meteorological observations made at the Observatory. Therefore, in addition to spatial temperature variation, the temporal aspect must also be considered. Many of the residential areas surrounding Armagh have developed since the 1960s and growth is continuing at the present time.

Recent research into correspondence relating to the Observatory weather station has brought to light earlier studies which have proved useful in assessing whether or not urban development has had an impact on observed temperatures.

A comparison was made between the Observatory and Loughgall (approx. 7 km to the NNE of the Observatory) over the period November 1957 to October 1963. Monthly means of maximum and minimum temperatures were determined for both sites and from these the mean monthly differences in temperature for each site were calculated for the six-year period. The comparison was repeated for the period January 1989 to December 1994. The year 1994 was chosen as the end of the recent period because the Loughgall weather station was re-sited in 1995. The station had previously remained on the same site since 1957.

Similar comparisons were made between Armagh and Annaghmore as well as between Armagh and Tandragee (approx. 19km to the N and 15km to the E respectively). Since the Annaghmore station was installed in 1980 and the Tandragee station in 1970, these comparisons could not be made over the same time span as that of Loughgall.

Taking each of the outlying stations in turn, it is apparent that the mean difference in both maxima and minima between Loughgall and Armagh has decreased slightly (by 0.20 and 0.05oC respectively) over the past 30 years. This is opposite to what would be expected as much of the urban growth around the Observatory site has occurred over the last 20-30 years. A similar temperature change pattern can be seen in the Annaghmore-Armagh comparison, albeit on a shorter time scale since no data is available from Annaghmore prior to 1980.

The Tandragee-Armagh comparison shows the reverse trend with the mean differences in minima increasing (by 0.45oC) over the given time interval. Further investigation reveals that the Tandragee weather station is located within a few metres of a large electricity substation, covering an area of several acres. It is arguable that the large volume of metal in and around the substation acts as a reservoir for solar radiation and also that the equipment itself produces a significant amount of heat. These factors make the results of any comparison with data from Tandragee highly questionable, especially bearing in mind the relatively small temperature differences observed.

The location of the Observatory relative to the urbanised area of Armagh raises a further interesting point. Farmland and playing fields extend country-ward to the northeast from the boundary of the Observatory grounds. In other words, the Observatory is not completely enclosed within the built-up area; a `corridor’ of open countryside extends into the grounds. The shape of an urban heat island corresponds closely with the geometry of the built up area with which it is associated (see Oke 1987) and, because the Observatory grounds lie country-ward of the urban boundary, it is possible that the urban heat island, in spite of its proximity, does not actually encroach into the Observatory grounds. The above comparison using historical data from neighbouring weather stations would support this case.

5. Conclusions

The data derived from the experimental work carried out in 1996 exhibits a mean difference in daily maximum temperatures of 0.11oC and 0.41oC in daily minimum temperatures between the site of the Observatory weather station and three similarly sited rural weather stations. However, recent research into the historical temperature records and comparisons with present day data from rural weather stations indicate that any temperature differences which existed between the Observatory site and the countryside 20-30 years ago have not increased over the intervening years. This is contrary to the situation which would be expected if urban development were to influence air temperatures at the Observatory, since much of the growth of Armagh has taken place since the 1960s and still continues.

In addition, the fact that there has been no urban encroachment into the Observatory grounds and that the grounds have not been separated from the adjacent farmland by any development suggests that the Observatory weather station lies outside the urban climatic boundary.

It is concluded that temperature observations made at Armagh Observatory have been unaffected by rapid urbanisation over the past three decades.

6. Acknowledgements

We wish to thank Mr Philip Doherty (retired), Mr Derek Ogle and Miss Elizabeth Warrick of Hillsborough Met. Office for the loan of and advice on the installation of the equipment used in the experiment. Our thanks are also due to Mr Tom Walker, Mr Peter Fegan, Mr John Sloan and Mr Ted Loughran for their permission to site the weather stations on their land. We also express our gratitude to Mr Donald Campbell of the Belfast Climate Office for the provision of rural meteorological data upon which our comparisons over the past 30 years are based.

Research at Armagh Observatory is grant-aided by the Department of Education for Northern Ireland.

Figures

Figure 1. The location of the four outlying, rural stations and the Observatory at Armagh.

Figure 2. Differences between the mean of the three rural stations (A,C and D) and the Observatory (O) against the temperature recorded at the Observatory. Upper panel – maximum, lower panel – minimum. Note that, apart from a zero point difference, there appears to be no trend with temperature.

Post navigation

33 thoughts on “UHI study of the UK Armagh Observatory”

Interesting, but the final line of the Conclusions states, “It is concluded that temperature observations made at Armagh Observatory have been unaffected by rapid urbanisation over the past three decades.”…this is misleading, suggesting the urbanisation had no effect on temps, when within the article itself it states, and I paraphrase ‘the sensors at the observatory are virtually unaffected by the nearby urbanisation due to the fact the observatory lies outside of the Urban Climate Zone’. So, if the sensors would have been placed within the core of where the urbanisation occurred rather than displaced from it with a large green field to the northeast and east then we would have likely seen more of a difference. But since they didn’t, we don’t…it’s just that last concluding line that is disingenuous and could be used by the enemy as fodder.

I cannot think of the effort to bring all of the U.S. stations into control, must be why GISS cuts the number of locations and does 1200km smoothing. They just thought about the task and then knowing they could predict the results, just adjust away.

“The mean difference in daily maxima between the Observatory and the mean of the three rural stations is found to be 0.11oC, whilst the difference in minima is 0.41oC, with the Observatory station warmer than the mean of the rural stations in both instances.”

I don’t get it.
The only thing that changed at the Observatory was urban development, UHI.
Otherwise, it would have the same temps as A,B,D.

“the thermometers at all three rural stations were tested by the Met.Office and were subsequently found to be accurate to within 0.1°C.”

Under ambient laboratory conditions. Not the same as outside in the sun and wind. Solar loading and wind speed effects are known to cause errors in temperature sensor readings. An example of this varying effect can be seen in Anthony’s own work.

Max Hugoson says:
August 26, 2010 at 6:23 pm
___________________
Agreed! I have sat on the back of a ute [“pickup” to the less enlightened ] on a still day and the changes in patches of temperatures while driving is quite surprising with maybe 2 or 3 degrees C changes over a hundred metres at times.
As an old glider pilot, the temperature changes in thermal cores again are quite large over distances of less than a hundred metres.

Our local rural, one sealed runway aerodrome based AWS is located some 150 metres down wind, across a dirt strip runway and the downwind in the prevailing westerly winds of a number of hangars covering about ten acres.
The surrounding country is all open, a very flat grain growing area and is 3 kms from the city of 13,000 to the SE.
Looking at the temp data and comparing it with another totally rural AWS some ten kilometres away, the A/D AWS seems to be about .2 /.3 C 150 metres away every time there is prevailing westerly wind blowing from across the hangar complex 150 metres upwind.
And this A/D has no jet traffic and is nearly all light aircraft with the occasional twin engined aircraft flying in.
On approach to one runway, an approach that is often directly down wind of the hangar complex, we usually strike some and occasionally considerable turbulence from the airflow across the hangars.
This turbulence in the right wind directions occurs around 500 metres down wind of the hangars and up to heights of about 200 feet.
In the light of my experiences, nobody will convince me that the proximity of trees, buildings , roads and etc within a 50 to 100 metres of a Surface Station will not affect the readings of that station at some time and will do so frequently and in unknown ways.

Not directly relevant But!
Dead flat terrain.
Research plots were sown in a flat terrain paddock of wheat of some 800 acres.
The plots were located about 120 metres due east, directly downwind of a patch of 10 metre high trees which only extended about 200 metres across the prevailing westerly winds and 120 metres directly upwind of the plots.
Two identical quality rain gauges were installed, one on the side of the plots nearest to the tree line and about 120 metres from the trees and the other about 50 metres further east or about 170 meters also directly in line with the first gauge and directly downwind of the trees.
This was on totally open, no obstructions, flat open Australian paddocks with no buildings or any other obstruction except the above mentioned patch of trees.
For 3 months those identical rain gauges measured a difference of some 20% difference in rainfall totals with the gauge nearest those trees 120 metres away having the consistently lower readings.
The gauge furtherest and about 170 metres from the trees was always the highest reading gauge.
We measured, we calibrated, we swapped gauges and we did every other thing we could think of to find the reasons but that difference of about 20% in rainfall amounts in that 50 metres distance between the identical gauges was completely consistent throughout that 3 month measuring period.
There was only one explanation and that was that those relatively small tree patch was having a very big influence with an abrupt shut off point even some 120 to 170 metres down wind of the trees.

No; 2
A dead flat paddock [ we can see the individual lights of our city some 25 kms across the countryside from the paddock on a clear night and the nearest hills / small mountains are 60 kilometres away other wise it is FLAT ] measuring 2 kms x 2 kms, no trees anywhere within 3/4’s of a kilometre and then only a very small house protection patch and no buildings of any sort as above, had 13 rain gauges installed in a pattern across the sown paddock to see what variation if any existed in rainfall across an area this size.
There was a consistently smaller or reduced amount of rainfall in one part of the paddock compared to the rest of the paddock.
The difference amounted to about 15% less rainfall in that one area of the paddock over the 4 winter rainfall months of the experiment.
Again there were absolutely no visible or apparent reasons or explanations, not even trees or any other obstructions to explain the variation in our rainfall differences and results over this obstruction free 4 sq kilometre area.

There are far, far more unknown influences and completely unknown factors and causes in measuring weather data than is generally realised and in light of what I have seen and measured and experienced as 72 year old farmer and life long pilot and glider pilot, I simply do not believe the supposed consistency and supposed accuracy in measurements between the surface stations that is claimed by the AGW advocacy research organisations.
Much, much less the total stupidity of trying to change the entire world’s social, economic and political structures to satisfy some crazy cult like ideology based completely on nothing more than these same corrupted surface station readings and data on which even more dubious unverifiable climate models are totally based on.

Dr Spencer’s analysis suggests much of the UHI effect occurs at the lower end of the urbanisation scale. That would be consistent with their finding of little change, if most of the UHI effect was already in place, with only a smaller increase since the ’60’s.

A tripling (let’s assume) of population density from about 400/km2 to 1200/km2 (roughly what it would’ve been at the time of the study) that would increase the UHI effect only by about 5%. If the minimum T measured UHI effect is 0.41 C for zero population up to 1200/km for the town, then the increase from the sixties to 1996 might add as little as 0.02 C to the Armagh UHI value. Very hard to measure such a small value.

I suspect also that the study period (1996) predates the great cheap airconditioner epidemic, although I have no idea if this has extended itself to Armargh. Interesting to know if this has had an effect on general UHI as well as for Anthony’s dirt file of poor stations.

What a coincidence. Just yesterday I asked for (and was promptly sent) their annual mean T since 2002 by Observatory staff for my project in preparation..
Comparing Armagh to CET, it seems that CET is also reasonably corrected for UHI. Their mutual difference shows no trend. For me, they are good representation of NH climate history since 1659, in one pass demolishing the hockey stick and claims about “dramatic and accelerating rate of climate change”.

I wonder when they were planted and how much denser those hedges have become since they matured and the additional co2 caused growth to increase. Even if they are cut to the same height throughout the period, a denser hedge is going to retain the ‘pond’ of cool night air better than a thinner hedge. They are going to retain sun warmed moist air better on a breezy day too, so maybe the effect on mean temp isn’t too important. If the hedges have gained height, low sun angle evaporation of overnight dew will be affected over the period too.

As a former glider pilot I can confirm the “lift” you get over a single road. Each rocky patch, grassy, wet, dry or paved area has uplift or downdraft all based on the differential temperatures from it. Jet fighters and bombers have difficulty flying ‘low and fast’ because the ‘bumpy’ ride makes it hard to control at mach anything. All that “bumpy” comes from thermal differences.

Comments on current temps being within range of previous centuries, the risks of using end of 19th century for baselines (exaggerates current warming), good correlation with other European temp records, and the effect of the NAO on temps. The current warming is described as ‘gradual’ in the context of 200 years of record – seems fair?

AIR TEMPERATURES AT ARMAGH OBSERVATORY, NORTHERN IRELAND,
FROM 1796 TO 2002

“Long-term trends are seen in both seasonal and annual mean temperatures, with spring and summer series relatively ﬂat compared with autumn and winter. Prior to 1820 we note that autumns and winters were cooler by ∼ 1 °C. Later, we note a signiﬁcant warming in the mid-19th century, which started in the late 1820s and continued till c. 1870. A cool interval at the end of the 19th century was followed by a period of rising mean temperatures that lasted till the mid-20th century. Finally, a slight cooling from 1960 to 1980 was followed by a gradual warming over the past two decades. In spite of the current warmer conditions, annual mean temperatures still remain within the range seen in the previous two centuries.

In the period of overlap, 1865–2002, we note that the features seen in the Armagh series are closely paralleled by features in the Northern Hemisphere mean temperature (Jones et al., 2001). The mid-19th century warm period, which is also seen in the central England series, has received relatively little attention. It is important to establish the reality of such 19th century warmings, because that century is frequently used as a baseline for modelling the 20th century climate. A baseline at the end of the 19th century, when conditions were noticeably cooler, would exaggerate the subsequent warming in the 20th century.

Mean maximum and minimum temperatures show a consistent downward trend in the DTR at Armagh since readings began in 1843. This may be a result of the increased cloudiness previously inferred from bright sunshine data for Ireland.

Comparison of the Armagh temperature series with the central England and Swedish series shows good agreement in their general trends; however, temperatures in Sweden show signiﬁcantly larger year-to-year variability. There is some evidence that the peaks in temperature in Armagh and central England occur a few years later than in Sweden.

A search for cyclic variability in the Armagh series identiﬁed a 7.8 year periodicity in winter and spring mean temperatures. This is undoubtedly due to the inﬂuence of the NAO, which contains power with the same periodicity. A similar periodicity was previously found in precipitation at Armagh.”

I have been to the Armagh Observatory. As the Wikipedia entry says, it is near the centre of the city, which is what I observed. The population of Armagh (and Northern Ireland) has changed very little over the last 150 years.

Armagh Observatory is a modern astronomical research institute with a rich heritage, based in Armagh, Northern Ireland. Around 25 astronomers are actively studying stellar astrophysics, the Sun, Solar System astronomy, and the Earth’s climate.
The Observatory is located close to the centre of the city of Armagh, adjacent to the Armagh Planetarium in approximately 14 acres (57,000 m2) of landscaped grounds known as the Armagh Astropark, and was founded in 1790 by Richard Robinson, Archbishop of Armagh.

It doesn’t take much thought to go from Armagh’s little UHI to a Global Anthroprogenic Heating Effect (adding up all the UHI’s and other changes people have made that impact Mother Nature). I’m sure that’s more along the lines of what the AGW climatologistie were originally thinking, but I guess some idiot talked them into limiting their focus to CO2 as the best way to make their point (and the simplest to measure). Unfortunately they latched on to a loser. If someone with a yin for weather knew a kid who was a wiz in programming ever wanted to make a bang in science, it’s easy to see that measuring and adding up all the UHI’s and coming up with the global impact would make a very very dramatic statement in a very NEW way. CO2 would be SOL and concrete and asphalt would we King of the Heap!

I still think that instead of digging holes and moving cities underground we need to build them on the bottom of the ocean and let the continents recover, besides, we’d have gravity on our side and wouldn’t have to burn so much coal. Know what I mean? Right?

This research does highlight the problems that temperature measurement has. It also highlights the foolishness of claims that a 0.1 degree rise in average temperature proves global warming. Satellite measurement should provide a more accurate data set but this will be affected by resolution and it did take some time before RSS and UAH came to an agreement over corrections. If you talk to any thermodynamicist they will tell you that to take the temperature of any system not at equilibrium will not produce an accurate result. Earth’s atmosphere is never at equilibrium.

Cross-referencing from the solar neutrino thread, I thought this quote was very relevant to climate issues: “But the more one has to bend [well-establish physics], the evidence has to be that much more scrutinized.”

With climate science being new, complex, and not obviously prone to bending physics, AGW didn’t need to produce any hard evidence before announcing itself as an irrefutable theory.

This very morning is one I’ve been waiting on here in NW Louisiana/E Texas. Cool(ish), low humidity, zero breeze.
I live in a rural parish south of Shreveport and work at a coal fired power plant in East Texas. On my drive I pass through Shreveport and with a few hundred yards of the NWS station for this region.

At the house, the weather gauge had 65F (poorly sited on the north side of the house, but in the shade and on white plaster which is over styrofoam – decent and trends well). The car thermometer had 67F. As I got away from the house and got good airflow over the car thermometer it dropped to 65F and matched the house thermo.

Once I left the area I live in which has a dozen homes within a 1/2 mile radius, the temp dropped to 63F and measured that consistently ’till within a mile of Shreveport. Then it climbed to 69F and wobbled between that and 67F ’till I was headed west on I-20 into E Texas. The reading dropped to 60 at one point in a low area surrounded by dense trees set back far from the interstate. We’re in a drought so there is little soil moisture to evaporate and stabilize the temp’s overnight, they’ll drop till the sun comes up. As I approached the power plant, the temp came up some, especially when I dropped down the hill to the lake basin area where the plant is sited. The temp rose to 70F.

Glad someone brought up Dr. Spencer’s UHI research. It’s real and does affect areas that have grown up over time, older year readings cooler than later year temperature readings.

Did a little background experimenting this summer. I have ended up with the conclusion that it is mainly the amount of rock, brick, cement, and asphalt that makes the UHI huge. These substances absorb a great amount of heat. Wood to a lesser degree. Soil on the other hand usually has moisture within a fraction of an inch from the surface. The heat that soil absorbs quickly causes sub-soil evaporation that keeps the soil’s temperature down, not so for dry substances, they take many, many hours to totally eject the energy from a day by internal conduction, especially if it was ever in direct sunlight, there is no evaporation to cool these surfaces.

My far backyard was always a few degrees, sometimes 8 degrees, cooler than near my home and especially around the back where there is a large cement patio. That part would stay warn in to the wee hours of the night and never equalized to the readings at the back of the lot over grassy soil by daybreak. Amazing. It is really there and sizeable.

We have not had rain for some 40 days, very usual here in late July and August, and the difference in these temperatures became closer and closer together as the soil dried out and became more like the cement and brick, little evaporation possible anymore.

As long as a thermometer isn’t nearby the exhaust of the condenser, like a weather stations, there is little change on a city-size scale, an A/C merely moves heat from the inside of a structure to outside of the structure. The house becomes a heat sink and the A/C exhaust a heat source. The biggest positive heat effect of this is from the some 5000+ watts it draws when running beside the heat removed from the interior. Just my thought. Don’t think you can blame overall UHI on air conditioners.

I know that is micro-climate effects but next summer I might document the same little experiment. Looks like some scientists would have already documented all of that work, don’t look forward to doing it again.

‘ “It is concluded that temperature observations made at Armagh Observatory have been unaffected by rapid urbanisation over the past three decades.”

And yet at the observatory they measure a 1/10th degree day time warmer, and a 1/2 degree night time warmer.
and offer no other explanation……… ‘

There might be something of a clue here:

The paper linked by Varco (Aug 27 1:03am) states:

“The mid-19th century warm period, which is also seen in the central England series, has received relatively little attention. It is important to establish the reality of such 19th century warmings, because that century is frequently used as a baseline for modelling the 20th century climate. A baseline at the end of the 19th century, when conditions were noticeably cooler, would exaggerate the subsequent warming in the 20th century.”
[AIR TEMPERATURES AT ARMAGH OBSERVATORY, NORTHERN IRELAND, FROM 1796 TO 2002. http://star.arm.ac.uk/preprints/445.pdf%5D

Dr Butler was interviewed by the BBC ten years ago and gave his views then:

‘Dr John Butler, the astronomer in charge of the project, told BBC News Online: “We can see global warming taking place over the past two centuries that suggests that changes in the Sun are at least partially responsible.” ‘
[http://news.bbc.co.uk/1/hi/sci/tech/1045327.stm]

A sun-cloud interaction of some kind is clearly implicated – mechanism uncertain – effects visible to all who approach the data with an open mind.

More evidence that climate change is multifactoral, with AGW as a component, not the dominant driver.

What is far more interesting is that Gisstemp does not use Armagh (probably the best long term record in the world) and instead uses data from the Met station at RAF Aldergove. Even more puzzling is that the station plot goes back to 1880!
No one flew an aircraft in Ireland prior to 1909. (Harry Ferguson of tractor fame, was the first, in a plane he built himself.)